Patent GB-862410-A (GB)
Title: Method and apparatus for carrying out exothermic reactions at high temperature and pressure
IPC: B01J8/00
Filed: 1959-07-09
Abstract: In the synthesis of methanol from CO and H2 in presence of a conventional zinc-chrome catalyst, the temperature in the catalyst bed is controlled by passing unreacted gas around but out of contact with the catalyst bed in a direction cocurrent with the flow of gas through the bed and by spacing baffles around the catalyst tubes so as to vary the amount of heat transferred from the reacted to the unreacted gas.  Specification 843,882 is referred to.ALSO:<PICT:0862410/III/1> A method of effecting catalytic exothermic gaseous reactions at high temperatures and pressures comprises introducing cool unreacted gases through at least one point in the converter, passing said gases in heat-exchange relationship with gases which have been heated by undergoing an exothermic catalytic reaction, passing the unreacted gases around but out of contact with the catalyst bed in a direction cocurrent with the flow of gases through the bed, reversing the flow of unreacted gases to pass through the bed but out of contact with the catalyst, then again reversing the flow of unreacted gases to direct them through the catalyst bed to react therein, collecting the reacted gases and passing them in heat exchange relationship with unreacted gases, and withdrawing the reacted gases from the converter.  It is preferred to (a) control the flow of the unreacted gas around the catalyst bed by baffles to vary heat transfer to the unreacted gas along the catalyst tube wall, and (b) introduce unreacted by-pass gas into the converter to mix with the partially preheated unreacted gas, or (c) withdraw hot reacted gases from the converter prior to passing in heat exchange relationship with unreacted gas, pass said gases to an external waste heat boiler, return said gases to the converter and pass them in heat-exchange relationship with cool unreacted gas, prior to withdrawing them from the converter.  The invention comprises also apparatus for carrying out the above method, a preferred embodiment being shown in Fig. 1, which is a pressure vessel containing catalyst section "A" and heat-exchanger section "B".  The cold unreacted gas introduced at 4 flows through the annulus formed between the shell and the liner 5, at the bottom of which the gas enters the heat-exchanger, flowing about the tubes 6 in counter-current with gas inside the tubes, and being directed about these tubes by baffles 7, thereafter passing through an annulus between 5 and baffle shells 11 and 12.  The gas flows around the catalyst tubes 13 and then up through the annulus formed by liners 17 and 18 and downwardly through a central tube containing the heating element 19 (used during startups).  The gas then flows upwardly through tubes 21 and downwardly through the catalyst bed 41 and thereafter through the tubes 6 and out of the converter by tubes 33 and 35. Additional unreacted gas from tube 36 is mixed with ionising gases from 4 at the hot end of the heat exchanger.  Fig. 2 (not shown) shows a modification in which the autoclave is modified so as to allow the hot gas leaving the catalyst tubes to be conducted to an external waste heat boiler, and then returned to the hot end of the heat exchanger.  The method of the invention is stated to be applicable to the synthesis of ammonia, the Fischer-Tropsch synthesis of hydrocarbon and the synthesis of methanol from CO and H2 (for which details of temperature control in the converter are given). Specification 843,822 is referred to.